The present invention relates to printing devices and more particularly to a novel rotatable print drum for printing variable data on paper documents at relatively high speeds as the documents pass through the printing location and wherein the print drum is provided with resilient self-aligning print wheels.
A large variety of paper document handling and counting devices are presently available in the market place and preferably have a capability of counting and stacking paper documents such as tickets, food coupons, bank notes, checks, and the like. The most desirable paper handling and counting devices preferably have the capability of accurately counting documents at high operating speeds.
In addition to the requirements of counting and stacking documents at high speed, many applications require a printing, cancelling or endorsing capability in which fixed data is imprinted upon each paper document as it undergoes a handling and counting operation, the printing being performed by means of a rotating print drum having raised characters arranged at predetermined locations about the periphery of the drum and adapted to rollingly engage an ink transfer roll and to engage the paper documents moving through the printing location. Many such applications further require that variable data be printed on one surface of each paper document. The printing operation must also be capable of being performed without in any way affecting (i.e., reducing) the high speed operation of the paper handling and counting machine.
In many such printing applications it is desirable and in some cases it is required that the print drum assembly have the capability of imprinting both fixed and variable data upon each paper document. This is important in applications wherein it is desired to indicate the date (day, month and year) on each document. This capability is quite important, for example, in banking operations wherein it is required that a cancellation stamp applied to each check include the date of cancellation. In such applications it is highly desirable to provide a print drum having a plurality of print wheels, each of which is capable of being simply and rapidly indexed to update the date stamp, typically on a daily basis.
Print drums presently available in the market place typically utilize print wheels mounted at spaced intervals about a print drum with each print wheel having a detent assembly for precisely and accurately indexing each portion of print matter on print wheel into the print position. One exemplary type of detent assembly employs a detent gear and a cooperating detent spring. Such devices, due to the number of components required to provide such an indexing capability, are large and cumbersome and often require servicing time of the order of 1 hour or more for the purpose of changing worn out, broken or outdated print wheels, the large amount of servicing time being required to perform the steps of: disassembling the print drum; removing and replacing the worn out, broken or outdated print wheel; and reassembly of the print drum. In reassembling the unit extreme care must be exercised to assure that the raised characters are replaced in the proper printing positions. This painstaking process, in addition to being time consuming, significantly increases the down-time in the paper handling and counting device.